IcyDwarf v14.6.2

-New "Compaction" routine that calculates the effects of compaction on
internal structure, given planetary materials, a mass, and a preliminary
structure. Either the 3rd order Birch-Murnaghan equation is solved
iteratively, or a rho = rho0 + c*P^n approximate equation is used
(Seager et al. 2007).
-Pressure is calculated in a simpler way in IcyDwarf. Remains to be
tested.